Electrolytic decomposition of saline solutions.



No. 736,982. PATENTED AUG. 25, 1903. A. B. LARCHAR.

ELECTROLYTIC DECOMPOSITION OF SALINE SOLUTIONS.

APPLICATION FILED OUT. 9. 1900 N0 MODEL. 3 SHEETS-SHEET l.

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No. 736,982. PATENTED A'II-G. 25..,1903,, I A. B. LARGHAR.

ELECTROLYTIC DECOMPOSITION OP SA-LINE SOLUTIONS.

APPLICATION IILED'00T.9, 1900.

N0 MODEL.

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No. 736,982. q PATENTED AUG. 25, 1903. A. B. LARGHAR.

ELECTROLYTIC DECOMPOSITION OF SALINE SOLUTIONS.

APPLIGATION FILED 0019, 1900.

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UNIT D STATES Patented August 25 1903.

PATENT OFFICE.

ARTHUR BTLARCHAR, OF OLDTOVVN, MAINE, ASSIGNOR TO THE PENOB- SCOT CHEMICAL FIBRE COMPANY, A CORPORATION OF MAINE.

ELECTROLYTIC DECOMPOSITION OF SALINE SOLUTIONS.

SPECIFICATION forming part of Letters Patent No. 736,982, dated August 25, I903.

Application filed October 9,1900. Serial No. 32,482. (No model.)

To all whom it may concern:

Be it known that I, ARTHUR B. LAROHAR, a citizen of the United States, and a resident of Oldtown, in the county of Penobscot and State of Maine, have invented a new and useful Improvement in the Electrolytic Decomposition of Saline Solutions, of which the-following is a full, clear, and exact description.

Myinvention includes a newand improved cell for the electrolytic decomposition of saline solutions, particularly solutions of common salt, and the production" therefrom of chlorin gas and caustic alkalies.

In the accompanying drawings I show a cell containing my invention and constructed in the form which I prefer for the embodiment of said invention at the'present time.

Figures 1, 2, and 3 are a plan view of the cell with portions broken away, Fig. 1 representing the cover on, Fig. 2 representing one end of the cell with the cover and upper portion of diaphragm removed, and Fig. 3 being a horizontal section of the opposite end, taken in the plane of the top of the tank and omitting the diaphragm. Fig. 4 .is an isometric view of the cover. Fig. 5 is a vertical longitudinal section on the line or x of Figs. 1, Fig. 6 is a cross-section on the line 1 y of Fig. 1.

Ct is a tank, preferably of steel boilerplate, which is open at the top and is large enough to provide a reservoir surrounding the cell.

The cathode is of peculiar and novel construction. It consists of a grating forming substantially a complete inclosure, constituting the side walls of the cell. As shown in the drawings, this grating is in sections b, b b and b forming the four sides of a parallelogram and secured together at the corners by posts 0', c c and 0 preferably of angle-iron. I prefer that each section of: the grating should be substantially flat, so that when combined they form a polygonal inolosure which serves not merely as the cathode, but possesses sufficient rigidity to act in conjunction with the corner-posts as the wall of the cell, supporting itselfand the diaphragm, which is stretched upon it, and in the example shown also the upper portion or cover of the cell from which the anodes depend. The grating composing the cathode consists of a series of bars or slats d d, &c., preferably of soft steel. Each of these slats is oblongin cross-section-say three-fourths of an inch wide by .049 inch thiekand stands preferably vertically and preferably substantially at right angles to the plane of the wall, of which it forms a part. The slats are spaced uniformly apart-say .035 inch between every two slats. These spaces constitute passages or channels leading outward through. the cathode 1 from the diaphragm. As shown, each passage or space is longer, measured from the diaphragm outward, than its width, measured between adjacent slats. As shown, also, each passage is excepting for the presence of the connecting-bolts and bushings substantially continuous from the lower to the upper portions of the cathode. The slats on each side of the cell are shown as held in the described position by a series of bolts or rods (2, 6, e c and 6 extending through two angle-iron posts and all of the intermediate slats. Washersf-are placed on each rod between every two slats, maintaining the proper distance apart. By having all the slats of equal thickness and all the washers of equal size a substantially uniform grating may thus be constructed, eXtendingsubst-antially withoutbreak or interruption all the way around the cell, so thatwith respect to the size of the cathode and the surfaces thereof exposed and the passages therethrough the brine percolating through the diaphragm may meet with substantially uniform conditions in all directions.

By the above construction a lamellar cathode is formed, which acts to divide the liquid into a great number of films which pass from the diaphragm out through the cathode into the receptacle which surrounds the cathode. In the course of this passage the liquid. by being in films is brought in most intimate contact with the layers of the cathode. At the same time the position of the passages, substantially radiating on all sides from the anodecompartment to the outer compartment, is most favorable to the free and direct circulation of the liquid and the'escape of the gas.

The floor of the cell is shown as being constructed of a series of angle-irons g g, &c.,

extending horizontally and transversely across from the bottom of the grating on one side to the bottom of the grating on the opposite side, each end of each angle-iron being secured in place between the lower ends of two slats by the bolt e by which the lower ends of the slats are combined.

h is a layer of Portland cement filling the spaces between the angle-irons g and between the lower ends of the slats, so as to form a continuous smooth floor.

The diaphragm consists, preferably, of asbestos paper, several thicknesses of which 0; i ji -say three or four thicknessesare placed around the walls of the cell, so as to break joints with each other, each layer forming a lap-joint with itself. The lower edge of the diaphragm is turned inwardly, so as to lie upon the cement floor, as shown. j is a layer of sand which covers the cement floor and extends over the lower edges of the diaphragm. At its upper edge the diaphragm is supported by the upper ends of the cathodeslats (1, over which it is folded outwardly and downwardly and against the outer edges of which its edge is secured by a surrounding frame 70. The cover Z, preferably consisting of a fiat slab of slate, rests on the diaphragm where it is folded over the tops of the slats, and the space an between the edges of the cover and the frame is preferably filled with cement.

The anodes consist, preferably, of a series of graphitized carbon slabs n n, &c., which extend downwardly through holes in the cover Z, in which they are properly luted. At their lower ends they may rest upon the sand layer j. Each anode is preferably inclined from top to bottom toward the diaphragm-wall adjacent to it for the purpose of making the length of the passage for the current through the electrolyte longest where the resistance of the carbon is least, and vice versa. In practice I have so inclined the nodes that the bottom of the anode was about one-eighth of an inch from the adjacent diaphragm-wall, while the top was about five-eighths of an inch therefrom.

Brine is supplied to the interior of the cell through the hard-rubber pipe 0 from a trough 19,0f non-conducting material,in which trough the brine from a reservoir q is kept at a substantially constant level by the centrifugal pump r and the overflow-pipe r. In this way the surface-level of the brine within the diaphragm is kept substantially at the line a, leaving a sufficient space betweenthe brinesurface and the cover for the free escape of the chlorin gas to the pipe 8, through which it passes to any suitable receiver. The interior of the cell above the brine-level is lined with lead for protection against the action of the chlorin.

The caustic-soda solution escapes from the reservoir in the tank (1 around the cell through the pipe 25 from an overflow-pipe 6, extending upwardly in said reservoir. Said overflowpipe is pivotally secured at its lower end, so that its overflow intake or mouth may be adjusted at various elevations in the dotted line t so as to permit the operator to adjust the surface-level of the liquid contained in the reservoir outside the cell relatively to the surface-level of the brine inside the cell. By this adjustment I utilize a very moderate and regulatable hydraulic pressure to gently press the liquid through the diaphragm in opposition to the tendency toward backward diffusion, while avoiding any degreeot' pressure which would produce such rapidity of percolation as to cause an undue escape of unconverted salt through the diaphragm and cathode-passages.

I have discovered that with an apparatus constructed substantially as above described I can by the simple adjustment relatively of.

the surface levels of the liquids, so as to maintain the inside level slightly above the outside level, secure conditions under which backward diffusion through the diaphragm of the caustic soda is substantially prevented, the escape of unconverted salt through the diaphragm is smallt'. 6., less than about fifty per cent.and an approximately theoretical efficiency is attained, accompanied by great durability of the diaphragm and other portions of the apparatus. In my experience I have found that with a total depth of brine of about twenty-four inches a difference in level of about one and one-half inches between the level a inside of the cell and the level a outside of the cell was sufficient to accomplish these results. The said adjustment also enables me to increase at will the pressure tending to: produce percolation of the brine through'the diaphragm. This is of the utmost importance. Efficiency requires that the rate of percolation be maintained; but the opposition of the diaphragm to percolation increases in use, because of the deposit of impurities from the brine and of particles of anode-carbon. By the adjustment of the liquid-levels it is constantly within the power of the attendant to compensate for the obstruction of such deposits, and thus prevent waste of power.

it is a pipe through which the contents of the cell may be drawn off at the bottom whenever desired for the purpose of testing or renewing the same.

Positive electric conductors are connected with the anodes and negative electric conductors with the cathode in any efficient manner.

In starting the reservoir in the tank around the cell is partially filled with water, and the cell is partially filled with brine. The electric current being turned on, the brine is decomposed, the chlorin thereby generated rising to the top of the cell and passing off through the pipe 8 to a tank or tower suitably arranged for its absorption. The metallic constituent of the brine combines at the passsages through the cathode with the water there present, forming a solution of caustic alkali. The hydrogen liberated in said passages passes freely up through the same and escapes at the open top of the tank. To enable a person skilled in the art more readily to re produce my said results, I will add the following concrete data as to the conditions under which I have operated with an apparatus constructed as above described. There were fourteen hundred slats each of the dimensions stated, twenty-two anodes each one and one-fourth inches by fourinches in cross section, and twenty square feet of diaphragm composed of three plies of asbestos paper each one thirty-second of an inch in thickness. The height of the cell was about thirty inches and the depth of brine therein about twenty-four inches. I used six hundred amperes of current at 3.8 voltage. The distance from the top of each anode to the adjacent side of the diaphragm at the top was about five-eighths of an inch and the distance at the bottom about one-eighth of an inch. Un-. der these conditions I secured the best results by maintaining the level of the liquid inside the cell about one and onehalf inches above the level outside the cell.

Although I have above described the limiting of the passage through the diaphragm of caustic soda and undecomposed salt by regulating the relative pressure of the liquids on opposite sides of the diaphragm and a means by which such regulation may be secured, I do not lay claim to the same in this application, since that invention is the subject of a separate application, Serial No. 126,402, filed by me October 9, 1902.

I claim- 1. In an apparatus for theelectrolysis of saline solutions, in combination, the anode, the diaphragm, and a cathode consisting of a series of gratings and means whereby said gratings are united at their edge; said cathode constituting a substantially vertical polygonal inclosure for said diaphragm.

2. In an apparatus for the electrolysis of saline solutions, in combination, the anode, the diaphragm, a cathode consisting of a series of gratings constituting a substantially vertical inclosure and support for said diaphragm and an imperforate bottom for said inclosure.

3. In an apparatus for the electrolysis of saline solutions, in combination, the anode, the diaphragm, a cathode consisting of a series of gratings constituting a substantially vertical inclosure for said diaphragm, an outside vessel and means whereby the level of the liquid inside and outside of said dia phragm is controlled to maintain the immersion of said cathode.

4:. In an apparatus for the electrolysis of saline solutions, in combination, the anode, the diaphragm, the cathode consisting of a series of gratings constituting a substantially vertical inclosui'e for said diaphragm, an imperforate bottom for said inclosure and an outside vessel.

5. In an apparatus for the electrolysis of saline solutions, in combination, the anode, the diaphragm, a cathode consisting of a series of gratings constituting a substantially verticallamellarinclosurefor said diaphragm, an imperforate bottom to said inclosure and an outside vessel; all substantially as described, whereby the liquid is divided by said lamellar cathode into thin films which flow horizontally away from said diaphragm to the body of liquid immersing the outside of said cathode.

ARTHUR B. LARGHAR. Witnesses:

OHAs. M. Downs, PATTRICK H. I-IUDIHAN. 

